Experimentally determine position of electron

How do we experimentally determine the position of an electron that is not bound to any atom and far away from all other influences including electromagnetic and gravitational fields? [Edit: what would the apparatus be?]

How do we experimentally determine the position of an electron that is not bound to any atom and far away from all other influences including electromagnetic and gravitational fields?

We can't.

It's a bit like determining the position of a bear in the woods. We may have an idea the bear is in there - seen little signs etc - but we don't know precisely where he is. If we lay a bear trap, and the bear walks into it, then we know the position of the bear.